US20100059592A1 - Aiming device - Google Patents
Aiming device Download PDFInfo
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- US20100059592A1 US20100059592A1 US12/519,087 US51908709A US2010059592A1 US 20100059592 A1 US20100059592 A1 US 20100059592A1 US 51908709 A US51908709 A US 51908709A US 2010059592 A1 US2010059592 A1 US 2010059592A1
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- light guide
- aiming device
- branches
- aiming
- luminous
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/18—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for optical projection, e.g. combination of mirror and condenser and objective
- G02B27/20—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for optical projection, e.g. combination of mirror and condenser and objective for imaging minute objects, e.g. light-pointer
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/04—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings formed by bundles of fibres
- G02B6/06—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings formed by bundles of fibres the relative position of the fibres being the same at both ends, e.g. for transporting images
Definitions
- the invention concerns an aiming device, in particular an aiming device that can be associated with an apparatus for image acquisition, such as, for example, an apparatus for reading optical information.
- optical information is used in this description and in the following claims to indicate any graphic representation having the function of storing a piece of information, whether coded or uncoded.
- a particular example of optical information is given by linear or two-dimensional optical codes, in which the information is coded by means of appropriate combinations of elements of preset form, for examples squares, rectangles or hexagons, of a dark colour, (usually black) separated by light elements (spaces, usually white), such as bar codes, stacked codes and two-dimensional codes in general, colour codes, etc.
- optical information further comprises other graphic forms, including printed characters (letters, numbers, etc.) and particular patterns (such as stamps, logotypes, signatures, fingerprints etc.).
- the term “optical information” comprises graphic representations detectable across the whole range of wavelengths, between infrared and ultraviolet, and thus not limited to the field of visible light.
- apparatus for image acquisition means a fixed or portable apparatus capable of acquiring images of objects or people, of subjects in general, and in particular of optical information, by means of a plurality of possible acquisition techniques.
- acquisition can take place by illuminating a subject, collecting with a suitable optical receiving system the light diffused by the object on a sensor consisting of an array of light-sensitive elements of a linear or matrix type, for example of the CCD or C-MOS type, and generating an image signal by means of an integrated or separate electronic system associated to the sensor.
- the image signal generated in analog or digital form; can then be processed by the same apparatus or in a separate image processing system.
- the image signal in digital form is decoded to extract the content information of the code.
- Apparatuses of this type are known as linear or matrix TV cameras or cameras, and when they read optical information, they are also known as code-reading devices of the “imager” type.
- the acquisition can be performed by illuminating a subject by scanning with one or more laser beams, by collecting the light diffused or reflected by the subject upon one or more photodiodes using an optical receiving system, and by generating, using a dedicated electronics, an electric image signal representing the diffusion/reflection of each point of the object that was struck by the laser beam during scanning.
- This signal is then processed and, in particular for apparatuses that read coded optical information, is digitalised and decoded. Apparatuses of this type are generally known as “laser scanners”.
- Optical code readers for example two-dimensional optical codes (Datamatrix, QR, PDF, Maxicode, etc.), in particular readers of the “imager” type with matrix sensors, are provided with aiming devices which as accurately as possible indicate to a user the Field of View (FoV) of the reader, that is, the framed area as the distance between the reader and the optical code varies.
- FoV Field of View
- the area aimed by the aiming device aiming area
- the user can be certain that if the optical code to be read is situated within the aiming area, it is indeed framed by the reader.
- Readers of the “laser scanner” type can also comprise aiming devices capable of indicating to the user the zone where scanning is performed.
- EP 0997760 describes an aiming device for an optical information reader comprising two lighting units, each of which comprising a light source, for example a LED, or a lamp, and a V-shaped light guide, arranged downstream of the respective light source in order to generate a pair of optical emission paths.
- a light source for example a LED, or a lamp
- V-shaped light guide arranged downstream of the respective light source in order to generate a pair of optical emission paths.
- Each V-shaped light guide comprises a pair of branches arranged at a predetermined angle.
- the light sources can be suitably inclined relative to a reading plane containing the optical information.
- the above-described aiming device generates four light beams defining on the reading plane vertices of a quadrilateral, which provides the user with a visual indication of a reading zone framed by the optical information reader.
- a drawback of the above-described aiming device is that a part of the light beam entering the V-shaped light guide of the aiming device escapes from it through the portion located where the light guide branches intersect.
- This part of the light beam produces an indefinite image on the reading plane, which image is thus added to the reference images produced by further portions of light beam that have traversed the branches of the V-shaped light guide and exit from these branches.
- the above-mentioned part of luminous beam creates a disturbance which not only prevents accurate indication of the reading zone framed by the optical information reader, but it can even cause confusion relative to the extension and position of the reading zone for an operator using the optical information reader.
- An object of the invention is to improve aiming devices for image acquisition apparatuses, in particular for apparatuses for reading optical information.
- a further object is to obtain an aiming device for image acquisition apparatuses that provides very clear and undisturbed reference images.
- a further object of the invention is to obtain an aiming device for image acquisition apparatuses comprising a light guide in which substantially all the luminous radiation entering the light guide contributes to defining reference images that facilitate the identification of an area framed by the image acquisition apparatus.
- an aiming device for an image acquisition apparatus, comprising light-emitting means and a light guide arranged for receiving a luminous radiation generated by said light-emitting means and for providing reference image means in an aiming zone, characterised in that said light guide comprises consecutive portions of light guide defining preferential directions of passage of said luminous radiation, each portion of light guide being inclined with respect to an adjacent portion of light guide.
- an aiming device can be obtained in which the luminous radiation advances within the light guide along a non-rectilinear path.
- the aiming device can emit the reference image means using emitting surface means of the light guide, positioned in any position whatsoever relative to the light source means.
- a reflection surface is interposed between adjacent portions of the light guide.
- the radiation entering the light guide can be in the form of a collimated luminous beam.
- substantially all the luminous radiation entering the light guide contributes to defining the reference image means.
- the reference image means since there is no significant dispersion of luminous radiation, the reference image means will be brighter, power of light emitting means being equal.
- the light guide comprises a plurality of branches and the light emitting means comprises a single source of light.
- the light guide can comprise five branches, four branches arranged for generating reference images positioned at the vertices of a quadrilateral and a fifth branch arranged for generating a reference image positioned in proximity of a centre of said quadrilateral.
- an aiming device for an image acquisition apparatus comprising light-emitting means and a light guide arranged for receiving a luminous radiation generated by said light-emitting means and for providing a plurality of reference images in an aiming zone, characterised in that said light guide comprises at least three branches, each of which emits a luminous beam arranged for generating a corresponding reference image of said plurality of reference images.
- the aiming pattern since it is identified by at least three distinct reference images—provides a user with a highly accurate indication.
- FIG. 1 is a perspective front view of the aiming device
- FIG. 2 is perspective rear view of the aiming device in FIG. 1 ;
- FIG. 3 is a perspective side view of the aiming device in FIG. 1 coupled to an objective-sensor assembly of an apparatus for reading optical information;
- FIG. 4 is a perspective side view of a branch of a light guide of the aiming device in FIG. 1 , showing an optical path of a luminous beam crossing said branch;
- FIG. 5 is a schematic perspective view of an aiming area identified by four luminous beams emitted by a first embodiment of the aiming device;
- FIG. 6 is the view of FIG. 5 showing an aiming area identified by five luminous beams
- FIG. 7 is the view of FIG. 5 , showing an aiming area identified by four luminous beams emitted by a second embodiment of the aiming device;
- FIG. 8 is the view of FIG. 5 , showing an aiming area identified by four luminous beams emitted by a third embodiment of the aiming device;
- FIG. 9 is a perspective rear view of a light guide having a square section
- FIG. 10 is the view of FIG. 9 showing a light guide having a circular section
- FIG. 11 is the view of FIG. 9 showing a light guide comprising optically inactive filling elements
- FIG. 12 is the view of FIG. 6 showing a particular structural solution for the light guide
- FIG. 13 is an irradiance map of the aiming device at a distance of 50 mm from an objective of an apparatus for reading optical information
- FIG. 14 is an irradiance map of the device in FIG. 13 at a distance of 100 mm from the objective of the apparatus for reading optical information;
- FIG. 15 is an irradiance map of the device in FIG. 13 at a distance of 150 mm from the objective of the apparatus for reading optical information;
- FIG. 16 is an irradiance map of the device in FIG. 13 at a distance of 200 mm from the objective of the apparatus for reading optical information;
- FIG. 17 is a map of irradiance of the device in FIG. 13 at a distance of 250 mm from the objective of the apparatus for reading optical information;
- FIG. 18 is a map of irradiance of the device of FIG. 13 at the distance of 300 mm from the objective of the apparatus for reading-optical information;
- FIG. 19 is a perspective schematic view of an apparatus for reading optical information.
- an aiming device 1 which comprises a light source, for example a laser 2 , coupled with a light guide 3 .
- the light source can comprise other lighting devices, such as a LED (Light Emitting Diode), or a lamp.
- LED Light Emitting Diode
- a lens 4 is interposed between the laser 2 and the light guide 3 .
- the lens 4 collimates the laser beam at the entrance of the light guide 3 , in such a way that rays entering the light guide 3 are parallel to one another.
- the lens 4 can be applied directly at an entrance end 5 of the light guide 3 .
- the light guide 3 comprises five branches, that is, a first branch 6 , a second branch 7 , a third branch 8 , a fourth branch 9 and a fifth branch 10 , each of which projects a reference image (in particular a substantially punctiform reference image, or spot) onto a defined aiming zone, for example, a reading plane 15 ( FIG. 5 ) comprising an optical information to be acquired.
- the optical information may comprise a linear or two-dimensional bar code, words, an image, or the like.
- the four branches projecting the peripheral spots onto the reading plane 15 terminate near a receiving objective 11 which focuses the framed code onto a sensor 12 with which an optical information reading device associated with the aiming device 1 is provided.
- End portions of the first branch 6 , the second branch 7 , the third 8 and the fourth branch 9 are arranged in such a way that they partially surround the receiving objective 11 .
- a 1 , A 2 , A 3 e A 4 respectively indicate exit surfaces of the first branch 6 , the second branch 7 , the third branch 8 and the fourth branch 9 , that is to say, the peripheral branches of the light guide 3
- AS indicates exit surface of the fifth branch 10 , that is of central branch of light guide 3 .
- a masking element is positioned around an active part of the lens 4 which collimates the laser beam, said masking element preventing all the rays emitted by the laser 2 that do not pass through the lens 4 from entering the light guide 3 , thus blocking unwanted rays/reflections.
- the laser beams that enter each branch of the light guide 3 undergo one or more internal reflections before leaving the light guide 3 .
- a suitably shaped diaphragm can further be provided, interposed between the laser 2 (or other light source) and an entrance of each branch of the light guide 3 in order to give a desired shape to each portion of collimated beam, thus generating a desired pattern as reference spot (e.g. triangle, circle, other geometrical form).
- the diaphragm can be interposed between the collimation lens 4 and the entrance of each branch, or it can be interposed between the source 2 and the collimation lens 4 .
- the diaphragm can be directly made on the collimation lens 4 , thus shading the zones involved so as to make said zones optically inactive.
- the light guide 3 can be customised, so as to obtain desired aiming patterns, without changing a mould with which the light guide 3 is produced (that is, without having to provide for each light guide 3 a section corresponding to the shape of the spot to be generated).
- a first laser beam 13 is shown entering the first branch 6 .
- the first branch 6 comprises a first portion 20 , a second portion 21 , a third portion 22 and a fourth portion 23 arranged in succession proceeding from the entrance end 5 towards the exit surface A 1 .
- the first portion 20 , the second portion 21 , the third portion 22 and the fourth portion 23 define preferential directions for passage of the first laser beam 13 , each portion being inclined in relation to an adjacent portion.
- Embodiments not shown of light guide can comprise branches provided with fewer or more than four portions.
- a reflection surface which directs the laser beam 13 coming from a more distant portion from the exit surface A 1 towards a portion which is nearer to the exit surface A 1 , that is, proceeding along the path defined by the first laser beam 13 , from a portion situated further upstream to a portion further downstream.
- a first reflection surface 24 is interposed between the first portion 20 and the second portion 21 , between the second portion 21 and the third portion 22 a second reflection surface 25 is interposed and between the third portion 22 and the fourth portion 23 a third reflection surface 26 is interposed.
- Each reflection surface 24 - 26 which also acts as a connecting surface between consecutive portions of the guide, is oriented at an angle of 45° with respect to longitudinal axes of two adjacent portions of the same branch. This angle has been chosen for two reasons.
- said angle is greater than the critical angle at which total internal reflection begins (this minimum angle depends on the material; said minimum angle for polycarbonate—of which the guide is made in the preferred embodiment—is approximately 39°. With an angle lower to this minimum angle, the collimated beam would have been transmitted in part through the connecting surfaces and thus out of the guide, therefore making the aiming device inefficient and even creating disturbance. It is therefore opportune for a guide made of optically transparent material that internal propagation of the beam is performed by total internal refection.
- the reflection surfaces 24 - 26 are inclined by 45°, the consecutive portions of each branch are at right angles to each other. Otherwise, in order to ensure that the beam proceeded parallel to the longitudinal axis of each portion, it would have been necessary to calculate the inclination of each portion with respect to the preceding portion evaluating the incidence and reflection angles on each connecting surface, that is, on each reflection surface 24 - 26 . Inclining at 45° the reflection surfaces 24 - 26 therefore simplifies calculation of paths followed by the rays.
- the first laser beam 13 follows a preset path P in such a way that when the laser beam 13 comes out of the light guide 3 , it defines a spot having a desired position in a very clear and accurate way—with modalities that will be described below.
- the first laser beam 13 since the first laser beam 13 has been collimated by the lens 4 , the first laser beam 13 traverses each branch of light guide 3 , remaining substantially parallel to a longitudinal axis of the branch.
- the preset path P is defined by a plurality of portions of path (a first portion of path P 1 associated with the first branch 20 , a second portion of path P 2 associated with the second branch 21 , a third portion of path P 3 associated with the third branch 22 and a fourth portion of path P 4 associated with the fourth branch 23 ) each of which is substantially linear.
- the first branch 6 is provided—downstream of the fourth portion of path P 4 —with a reflection surface R 1 which further reflects the laser beam 13 before the latter leaves the first branch 6 through the exit surface A 1 .
- the reflection surface R 1 is the last reflection surface of the first branch 6 in which there is an internal reflection.
- the reflection surface R 1 is suitably inclined so that a portion of beam 14 of the first laser beam 13 leaving the light guide 3 through the exit surface Al has a desired direction.
- the exit surface A 1 is perpendicular to the portion of beam 14 leaving the first branch 6 .
- the direction of the portion of beam 14 leaving the first branch 6 is independent of the refractive index of the material of which the light guide 3 is made.
- Each branch of the light guide 3 projects a luminous spot onto the plane of code.
- the spatial orientation of the last reflection surface (indicated by R 1 in the case of first branch 6 ) and of the exit surface (indicated by A 1 in the case of first branch 6 ) a pattern formed by five spots is obtained, four peripheral spots (forming a quadrilateral) and a central spot.
- the shape and dimension of each of these spots substantially correspond to the shape and dimension of the corresponding exit surface of the respective branch, or to the shape and dimension of the aperture of the diaphragm associated with said branch.
- a peripheral projection pattern is defined on the plane of code.
- a hollow light guide 3 made of a non-transparent material can be used, while all the internal reflection surfaces ( 24 - 26 for branch 6 ) and all the last reflection surfaces (R 1 for the branch 6 and R 2 -R 5 for the branches 7 - 10 ) are coated with, or made of, a reflecting material (e.g. a mirror). In this variant it is not necessary to provide the exit surfaces A 1 -A 5 .
- Embodiments of the light guide can comprise more or fewer than five branches.
- four branches can be provided which generate four spots arranged such as to identify vertices of a quadrilateral.
- This embodiment is similar to the previously described embodiment, but lacks the central branch, i.e. the fifth branch 10 .
- a further embodiment can comprise three branches that generate three spots, two of which are arranged such as to identify opposite vertices of a quadrilateral and a third of which is arranged such as to identify a central area of the quadrilateral.
- the three branches can be arranged such as to identify the three vertices of a triangle.
- a still further embodiment can comprise two branches that generate two spots arranged such as to identify opposite vertices of a quadrilateral.
- a still further embodiment can comprise two branches that generate two substantially aligned spots.
- This embodiment is particularly advantageous when linear optical information is to be acquired.
- the exit surfaces A 1 -A 4 are so oriented that the pattern projected by the four peripheral branches of the light guide 3 delimits, on the reading plane 15 , a rectangular surface having vertices B 1 -B 4 , which identifies the aiming area 16 .
- the four laser beams coming out of the peripheral branches of the light guide 3 intersect each other at a point H, situated on the optical axis of the receiving objective 11 at a distance h from the receiving objective 11 .
- the aiming area B 1 -B 4 is always contained within the reader field of view of the reader (identified in FIG. 5 by a further rectangular surface having the vertices 11 - 14 ).
- the framed area 17 always contains the aiming area 16 for every code/reader distance.
- the relation between the aiming area 16 and the framed area 17 is inverted, with the former containing the latter.
- the spot generated by the fifth branch 10 (that is by the central branch of the light guide 3 which comprises the exit surface A 5 ) has not been shown on the reading plane 15 .
- the fifth branch 10 generates a spot that is situated in proximity of the centre of the aiming area 15 .
- the spatial orientation of the last reflection surface R 5 of fifth branch 10 and that of exit surface A 5 are such that a fifth laser beam, coming out of fifth branch 10 , intercepts the optical axis of the receiving objective 11 at only one point—indicated by C 5 in FIG. 613 at a distance c from the receiving objective.
- the fifth beam is misaligned with respect to optical axis of receiving objective 11 and generates the spot B 5 on the reading plane 15 .
- the exit surfaces A 1 -A 4 are oriented in such a way that the pattern projected by the four peripheral branches of the light guide 3 delimits, on the reading plane 15 , a rectangular surface having vertices B 1 -B 4 which identify the aiming area 16 .
- the four laser beams coming out of the peripheral branches have no point of intersection.
- the aiming area 16 and the framed area 17 substantially coincide at a distance k from receiving objective 11 .
- the aiming area 16 always contains the framed area 17 while, for code-reader distances greater than distance k, the aiming area 1 . 6 is always contained within the framed area 17 .
- FIG. 7 does not show the spot generated on the reading plane 15 by the central branch of the guide, the position of which remains unchanged with respect to the first configuration previously described.
- the operator using the reading device at code-reader distances smaller than k cannot be certain that a code belonging to aiming area 16 is really framed and therefore acquired by the reader sensor and then decoded. In fact, a code near an edge of the aiming area 16 could be left out (also only partially) of the framed area 17 .
- the codes to be read have generally small dimensions and the indication given by the spot generated by the central branch of the guide constitutes a sufficient reference for the operator.
- the exit surfaces A 1 -A 4 are so oriented that the pattern projected by the four peripheral branches of the light guide 3 delimits, on the reading plane 15 , a rectangular surface having vertices B 1 -B 4 which identify the aiming area 16 .
- the four laser beams coming out of the peripheral branches intersect each other in pairs, or two by two.
- the aiming area is contained within the framed area 17 .
- the framed area 17 With distances of the receiving objective 11 from the code that are greater than distance w, the framed area 17 always contains the aiming area 16 , while with distances of the receiving objective 11 from the code which are smaller than distance w it is not possible to be certain whether the framed area 17 contains, or is contained in, the aiming area 16 .
- FIG. 8 does not show the spot generated on the reading plane 15 by the central branch of the guide, the position of which remains unvaried with respect to the above described first and the second configurations.
- fillings 19 can be inserted within the light guide 3 , said fillings being optically inactive portions arranged for increasing the mechanical resistance of the light guide 3 , leaving unaltered the optically active surfaces.
- the light guide 3 can comprise portions of guide having a circular section.
- the light guide 3 can comprise portions of guide having a square or rectangular cross-section.
- the light guide 3 comprises portions of guide having a square section of 1.4 mm ⁇ 1.4 mm.
- the light guide 3 similarly to what is shown in FIG. 11 , comprises optically inactive fillings to increase mechanical stability.
- the exit surfaces A 1 -A 4 of the four peripheral branches of light guide 3 are arranged according to the first configuration which has been described with reference to FIGS. 5 and 6 .
- the laser beams coming out of the four peripheral branches of the light guide 3 intersect one another at the point H′ of the optical axis which is less than 30 mm from the receiving objective 11 . If the distance between receiving objective 11 and exit glass of the reader is greater than h′, the above-mentioned laser beams are always contained within the framed area 17 .
- the laser beam coming out of the central branch intersects the optical axis at the point C 5 ′ which is approximately 150 mm from the receiving objective 11 .
- the light guide of the preferred embodiment above described has been modelled using the TracePro® ray-tracing simulation program.
- the results obtained from the simulation program match those calculated during the design process very well.
- a beam of parallel rays (those coming out of the collimating lens) strikes the five branches and an irradiance map on the plane of code was obtained in, relation to the distance from the objective.
- the results are illustrated in FIGS. 13 to 18 .
- B 1 ( ⁇ 64.8, ⁇ 53.5)
- B 1 S ( ⁇ 68.2, ⁇ 53.3)
- B 2 (68.4, ⁇ 53.5)
- B 2 S (68.2, ⁇ 53.3)
- B 4 ( ⁇ 64.8, 53.5)
- B 4 S ( ⁇ 68.2, 53.6)
- an optical information reader 30 With reference to FIG. 19 , interior of an optical information reader 30 is schematically shown.
- the light guide 3 in the preferred embodiment in FIG. 12 , can be fixed inside the reader 30 so as to ensure correct coupling with a laser diode 27 with which the laser 2 is provided.
- Reophores of laser diode 27 are soldered on a PCB 29 on which the sensor 12 is also mounted, which sensor is in turn contained within an optical chamber not illustrated in FIG. 19 .
- the laser diode 27 is mounted perpendicular to the PCB 29 and correct positioning thereof is ensured by a tubular element 28 which contains the laser diode and is made for example of a plastic material.
- the laser diode 27 is inserted in a first end 31 of the tubular element 28 .
- the base of the tubular element 28 is in turn fixed—for example by a pair of screws—to the PCB 29 .
- the tubular element 28 is longer than the laser diode 27 : thus it is possible to insert the entrance end 5 of the light guide 3 (the one provided with the collimation lens 4 ) within a second end 32 of the tubular element 28 , opposite the first end 31 .
- the light guide 3 can be held in position with respect to tubular element 28 by means of one or more threaded connecting elements or by a special assembly tool (template).
- the distance between the laser diode 27 and the lens 4 is such that the laser beam entering the light guide 3 is well collimated.
- an assembly tool (template) can be made that is capable of moving the light guide 3 forwards and backwards so as to identify (and afterwards to fix) an optimal laser diode 27 —lens 4 distance by checking the collimation of the beam coming out of the guide.
- a second way consists of fixing the light guide 3 within the tubular element 28 in such a way that the laser diode 27 —lens 4 distance is near the optimal distance (the light guide 3 is thus solidly connected to the tubular element 28 ). Then an assembly tool (template) is used to move the laser diode 27 backwards and forwards with respect to the PCB 29 by means of the play provided by the length of reophores; once the optimal distance has been found—always by checking the collimation of the laser beam coming out of the light guide—the position of the laser diode 27 on the PCB 29 is fixed by soldering the reophores.
- the use of the light guide 3 is advantageous in manufacturing the reader 30 : the laser diode 27 is in fact soldered to the same PCB 29 on which the sensor 12 is also mounted (there is no need for a wiring connection) and the collimation of the aiming device can also be carried out using for example one of the two ways described, also in a “remote” manner with respect to the rest of optic chamber.
- the optical chamber and the tubular element containing the laser diode could be made in a single piece, moulded in plastic (or cast in metal).
- the apparatus for reading optical information comprising the device of the invention in the possible embodiments thereof can be housed in a casing that can be held by an operator and thus be portable, or be in a fixed casing for example for reading applications at points of sale (POS) where the operator passes objects in front of a window of the apparatus for reading optical information, and the optical code to be read faces the window.
- POS points of sale
- the reading apparatus can also be fixed at a conveyor belt, or other means for transferring objects, for use in industrial optical information reading applications associated to object in motion even at high speeds. Applications of this type can also be used for control of production lines or recognition, tracing and sorting of objects and packages.
- the portable and fixed reading apparatuses can be of the “imager” or the “laser scanner” type.
- the aiming device of the invention can be advantageously used in image acquisition apparatuses in general, where it can be useful to indicate clearly the framed zone to an operator, so that the image acquisition apparatus can be positioned correctly.
- Apparatuses of this type can be for example micro-cameras lacking a display for observing the framed area, or fixed TV cameras for acquiring images of objects in motion on conveyor belts and for determining their size or shape characteristics or for control and surveillance systems.
Abstract
Description
- The invention concerns an aiming device, in particular an aiming device that can be associated with an apparatus for image acquisition, such as, for example, an apparatus for reading optical information.
- The expression “optical information” is used in this description and in the following claims to indicate any graphic representation having the function of storing a piece of information, whether coded or uncoded. A particular example of optical information is given by linear or two-dimensional optical codes, in which the information is coded by means of appropriate combinations of elements of preset form, for examples squares, rectangles or hexagons, of a dark colour, (usually black) separated by light elements (spaces, usually white), such as bar codes, stacked codes and two-dimensional codes in general, colour codes, etc. More in general the term “optical information” further comprises other graphic forms, including printed characters (letters, numbers, etc.) and particular patterns (such as stamps, logotypes, signatures, fingerprints etc.). The term “optical information” comprises graphic representations detectable across the whole range of wavelengths, between infrared and ultraviolet, and thus not limited to the field of visible light.
- In the present description and in the following claims the expression “apparatus for image acquisition” means a fixed or portable apparatus capable of acquiring images of objects or people, of subjects in general, and in particular of optical information, by means of a plurality of possible acquisition techniques.
- For example, acquisition can take place by illuminating a subject, collecting with a suitable optical receiving system the light diffused by the object on a sensor consisting of an array of light-sensitive elements of a linear or matrix type, for example of the CCD or C-MOS type, and generating an image signal by means of an integrated or separate electronic system associated to the sensor. The image signal, generated in analog or digital form; can then be processed by the same apparatus or in a separate image processing system.
- Typically, in apparatuses for reading coded optical information, such as bar codes, the image signal in digital form is decoded to extract the content information of the code.
- Apparatuses of this type are known as linear or matrix TV cameras or cameras, and when they read optical information, they are also known as code-reading devices of the “imager” type.
- According to another technique, the acquisition can be performed by illuminating a subject by scanning with one or more laser beams, by collecting the light diffused or reflected by the subject upon one or more photodiodes using an optical receiving system, and by generating, using a dedicated electronics, an electric image signal representing the diffusion/reflection of each point of the object that was struck by the laser beam during scanning. This signal is then processed and, in particular for apparatuses that read coded optical information, is digitalised and decoded. Apparatuses of this type are generally known as “laser scanners”. Instead of capturing an image with a single simultaneous acquisition of all the light-sensitive elements (“in parallel”), as in TV cameras and “imager” reading devices, “laser scanners” capture the image of the object sequentially during the scanning process, one instant after another (“in series”). Optical code readers, for example two-dimensional optical codes (Datamatrix, QR, PDF, Maxicode, etc.), in particular readers of the “imager” type with matrix sensors, are provided with aiming devices which as accurately as possible indicate to a user the Field of View (FoV) of the reader, that is, the framed area as the distance between the reader and the optical code varies. In particular, it is preferable that the area aimed by the aiming device (aiming area) is always included within the area actually framed. In this way, the user can be certain that if the optical code to be read is situated within the aiming area, it is indeed framed by the reader.
- Readers of the “laser scanner” type, especially those that use lasers with non-visible wavelengths, can also comprise aiming devices capable of indicating to the user the zone where scanning is performed.
- EP 0997760 describes an aiming device for an optical information reader comprising two lighting units, each of which comprising a light source, for example a LED, or a lamp, and a V-shaped light guide, arranged downstream of the respective light source in order to generate a pair of optical emission paths. Each V-shaped light guide comprises a pair of branches arranged at a predetermined angle.
- Furthermore, the light sources can be suitably inclined relative to a reading plane containing the optical information.
- As a result, the above-described aiming device generates four light beams defining on the reading plane vertices of a quadrilateral, which provides the user with a visual indication of a reading zone framed by the optical information reader.
- A drawback of the above-described aiming device is that a part of the light beam entering the V-shaped light guide of the aiming device escapes from it through the portion located where the light guide branches intersect.
- This part of the light beam produces an indefinite image on the reading plane, which image is thus added to the reference images produced by further portions of light beam that have traversed the branches of the V-shaped light guide and exit from these branches. In other words, the above-mentioned part of luminous beam creates a disturbance which not only prevents accurate indication of the reading zone framed by the optical information reader, but it can even cause confusion relative to the extension and position of the reading zone for an operator using the optical information reader.
- Only the light rays emitted by the light source, which have a substantially parallel direction to one of the branches of the V-shaped light guide contribute to forming the above-mentioned further portions of light ray, and consequently the reference images on the reading plane. All the other light rays emitted by the light source follow an uncontrolled path within the light guide and can leave the light guide in equally uncontrolled directions, forming the indefinite image referred to above. In addition, the quantity of these rays that are substantially parallel to one of the branches of the guide is very small, or even negligible, compared to the total number of rays emitted by the source, so that it is difficult for an operator to identify visually the above-mentioned reference images on the reading plane.
- An object of the invention is to improve aiming devices for image acquisition apparatuses, in particular for apparatuses for reading optical information.
- A further object is to obtain an aiming device for image acquisition apparatuses that provides very clear and undisturbed reference images.
- A further object of the invention is to obtain an aiming device for image acquisition apparatuses comprising a light guide in which substantially all the luminous radiation entering the light guide contributes to defining reference images that facilitate the identification of an area framed by the image acquisition apparatus.
- In a first aspect of the invention, an aiming device is provided for an image acquisition apparatus, comprising light-emitting means and a light guide arranged for receiving a luminous radiation generated by said light-emitting means and for providing reference image means in an aiming zone, characterised in that said light guide comprises consecutive portions of light guide defining preferential directions of passage of said luminous radiation, each portion of light guide being inclined with respect to an adjacent portion of light guide.
- Owing to this aspect of the invention, an aiming device can be obtained in which the luminous radiation advances within the light guide along a non-rectilinear path. In this way, the aiming device can emit the reference image means using emitting surface means of the light guide, positioned in any position whatsoever relative to the light source means.
- In an embodiment, a reflection surface is interposed between adjacent portions of the light guide.
- In another embodiment, the radiation entering the light guide can be in the form of a collimated luminous beam.
- It is therefore possible to obtain an aiming device wherein there is a reduced risk that portions of luminous radiation beyond those forming the reference image means will escape from the light guide, that is, portions of luminous radiation that could create a disturbance in the aiming zone.
- In particular, substantially all the luminous radiation entering the light guide contributes to defining the reference image means.
- In this way, since there is no significant dispersion of luminous radiation, the reference image means will be brighter, power of light emitting means being equal.
- In a still further embodiment, the light guide comprises a plurality of branches and the light emitting means comprises a single source of light.
- In this case, a very economical aiming device can be obtained, since one single light source generates a plurality of reference images.
- In particular, the light guide can comprise five branches, four branches arranged for generating reference images positioned at the vertices of a quadrilateral and a fifth branch arranged for generating a reference image positioned in proximity of a centre of said quadrilateral.
- In a second aspect of the invention, an aiming device is provided for an image acquisition apparatus comprising light-emitting means and a light guide arranged for receiving a luminous radiation generated by said light-emitting means and for providing a plurality of reference images in an aiming zone, characterised in that said light guide comprises at least three branches, each of which emits a luminous beam arranged for generating a corresponding reference image of said plurality of reference images.
- Owing to this aspect of the invention, it is possible to obtain a plurality of reference images using a single light source.
- The aiming pattern—since it is identified by at least three distinct reference images—provides a user with a highly accurate indication.
- The invention will be better understood and carried into effect with reference to the attached drawings, in which some embodiments are shown by way of non-limiting example, in which:
-
FIG. 1 is a perspective front view of the aiming device; -
FIG. 2 is perspective rear view of the aiming device inFIG. 1 ; -
FIG. 3 is a perspective side view of the aiming device inFIG. 1 coupled to an objective-sensor assembly of an apparatus for reading optical information; -
FIG. 4 is a perspective side view of a branch of a light guide of the aiming device inFIG. 1 , showing an optical path of a luminous beam crossing said branch; -
FIG. 5 is a schematic perspective view of an aiming area identified by four luminous beams emitted by a first embodiment of the aiming device; -
FIG. 6 is the view ofFIG. 5 showing an aiming area identified by five luminous beams; -
FIG. 7 is the view ofFIG. 5 , showing an aiming area identified by four luminous beams emitted by a second embodiment of the aiming device; -
FIG. 8 is the view ofFIG. 5 , showing an aiming area identified by four luminous beams emitted by a third embodiment of the aiming device; -
FIG. 9 is a perspective rear view of a light guide having a square section; -
FIG. 10 is the view ofFIG. 9 showing a light guide having a circular section; -
FIG. 11 is the view ofFIG. 9 showing a light guide comprising optically inactive filling elements; -
FIG. 12 is the view ofFIG. 6 showing a particular structural solution for the light guide; -
FIG. 13 is an irradiance map of the aiming device at a distance of 50 mm from an objective of an apparatus for reading optical information; -
FIG. 14 is an irradiance map of the device inFIG. 13 at a distance of 100 mm from the objective of the apparatus for reading optical information; -
FIG. 15 is an irradiance map of the device inFIG. 13 at a distance of 150 mm from the objective of the apparatus for reading optical information; -
FIG. 16 is an irradiance map of the device inFIG. 13 at a distance of 200 mm from the objective of the apparatus for reading optical information; -
FIG. 17 is a map of irradiance of the device inFIG. 13 at a distance of 250 mm from the objective of the apparatus for reading optical information; -
FIG. 18 is a map of irradiance of the device ofFIG. 13 at the distance of 300 mm from the objective of the apparatus for reading-optical information; -
FIG. 19 is a perspective schematic view of an apparatus for reading optical information. - With reference to
FIGS. 1 to 3 , an aimingdevice 1 is shown which comprises a light source, for example alaser 2, coupled with alight guide 3. - Alternatively, the light source can comprise other lighting devices, such as a LED (Light Emitting Diode), or a lamp.
- A
lens 4 is interposed between thelaser 2 and thelight guide 3. Thelens 4 collimates the laser beam at the entrance of thelight guide 3, in such a way that rays entering thelight guide 3 are parallel to one another. Thelens 4 can be applied directly at anentrance end 5 of thelight guide 3. - The
light guide 3 comprises five branches, that is, afirst branch 6, asecond branch 7, athird branch 8, afourth branch 9 and afifth branch 10, each of which projects a reference image (in particular a substantially punctiform reference image, or spot) onto a defined aiming zone, for example, a reading plane 15 (FIG. 5 ) comprising an optical information to be acquired. As already stated, the optical information may comprise a linear or two-dimensional bar code, words, an image, or the like. - As shown in
FIG. 3 , the four branches projecting the peripheral spots onto the reading plane 15 (that is thefirst branch 6, thesecond branch 7, thethird branch 8 and the fourth branch 9) terminate near a receivingobjective 11 which focuses the framed code onto asensor 12 with which an optical information reading device associated with the aimingdevice 1 is provided. - End portions of the
first branch 6, thesecond branch 7, the third 8 and thefourth branch 9 are arranged in such a way that they partially surround the receivingobjective 11. A1, A2, A3 e A4 respectively indicate exit surfaces of thefirst branch 6, thesecond branch 7, thethird branch 8 and thefourth branch 9, that is to say, the peripheral branches of thelight guide 3, while AS indicates exit surface of thefifth branch 10, that is of central branch oflight guide 3. - A masking element, not shown, is positioned around an active part of the
lens 4 which collimates the laser beam, said masking element preventing all the rays emitted by thelaser 2 that do not pass through thelens 4 from entering thelight guide 3, thus blocking unwanted rays/reflections. - The laser beams that enter each branch of the
light guide 3 undergo one or more internal reflections before leaving thelight guide 3. - A suitably shaped diaphragm can further be provided, interposed between the laser 2 (or other light source) and an entrance of each branch of the
light guide 3 in order to give a desired shape to each portion of collimated beam, thus generating a desired pattern as reference spot (e.g. triangle, circle, other geometrical form). The diaphragm can be interposed between thecollimation lens 4 and the entrance of each branch, or it can be interposed between thesource 2 and thecollimation lens 4. In particular, the diaphragm can be directly made on thecollimation lens 4, thus shading the zones involved so as to make said zones optically inactive. - In this ways, the
light guide 3 can be customised, so as to obtain desired aiming patterns, without changing a mould with which thelight guide 3 is produced (that is, without having to provide for each light guide 3 a section corresponding to the shape of the spot to be generated). - With reference to
FIG. 4 , afirst laser beam 13 is shown entering thefirst branch 6. - The
first branch 6 comprises afirst portion 20, asecond portion 21, athird portion 22 and afourth portion 23 arranged in succession proceeding from theentrance end 5 towards the exit surface A1. - The
first portion 20, thesecond portion 21, thethird portion 22 and thefourth portion 23 define preferential directions for passage of thefirst laser beam 13, each portion being inclined in relation to an adjacent portion. - Embodiments not shown of light guide can comprise branches provided with fewer or more than four portions.
- Between each pair of adjacent portions a reflection surface is provided which directs the
laser beam 13 coming from a more distant portion from the exit surface A1 towards a portion which is nearer to the exit surface A1, that is, proceeding along the path defined by thefirst laser beam 13, from a portion situated further upstream to a portion further downstream. - In particular, between the
first portion 20 and the second portion 21 afirst reflection surface 24 is interposed, between thesecond portion 21 and the third portion 22 asecond reflection surface 25 is interposed and between thethird portion 22 and the fourth portion 23 athird reflection surface 26 is interposed. - Each reflection surface 24-26, which also acts as a connecting surface between consecutive portions of the guide, is oriented at an angle of 45° with respect to longitudinal axes of two adjacent portions of the same branch. This angle has been chosen for two reasons.
- Firstly, said angle is greater than the critical angle at which total internal reflection begins (this minimum angle depends on the material; said minimum angle for polycarbonate—of which the guide is made in the preferred embodiment—is approximately 39°. With an angle lower to this minimum angle, the collimated beam would have been transmitted in part through the connecting surfaces and thus out of the guide, therefore making the aiming device inefficient and even creating disturbance. It is therefore opportune for a guide made of optically transparent material that internal propagation of the beam is performed by total internal refection.
- Secondly, if the reflection surfaces 24-26 are inclined by 45°, the consecutive portions of each branch are at right angles to each other. Otherwise, in order to ensure that the beam proceeded parallel to the longitudinal axis of each portion, it would have been necessary to calculate the inclination of each portion with respect to the preceding portion evaluating the incidence and reflection angles on each connecting surface, that is, on each reflection surface 24-26. Inclining at 45° the reflection surfaces 24-26 therefore simplifies calculation of paths followed by the rays.
- Inside the
first branch 6, thefirst laser beam 13 follows a preset path P in such a way that when thelaser beam 13 comes out of thelight guide 3, it defines a spot having a desired position in a very clear and accurate way—with modalities that will be described below. - In particular, since the
first laser beam 13 has been collimated by thelens 4, thefirst laser beam 13 traverses each branch oflight guide 3, remaining substantially parallel to a longitudinal axis of the branch. - As a result, the preset path P is defined by a plurality of portions of path (a first portion of path P1 associated with the
first branch 20, a second portion of path P2 associated with thesecond branch 21, a third portion of path P3 associated with thethird branch 22 and a fourth portion of path P4 associated with the fourth branch 23) each of which is substantially linear. - Apart from absolutely irrelevant losses, due for example to border effects on surfaces delimiting each of the five branches 6-10 of the guide and in the contact/separation zone between adjacent branches of the guide, all the luminous radiation which defines the
first laser beam 13 contributes to form said spot. In other words, no portions of the luminous radiation defining thefirst laser beam 13 leave thefirst branch 6 through any surface except the exit surface A1, and therefore no indefinite image or disturbance is generated on the readingplane 15 that would make it difficult, or even impossible, to identify univocally an aiming area 16 (FIG. 5 ) identified by the aimingdevice 1. Thefirst branch 6 is provided—downstream of the fourth portion of path P4—with a reflection surface R1 which further reflects thelaser beam 13 before the latter leaves thefirst branch 6 through the exit surface A1. - The reflection surface R1 is the last reflection surface of the
first branch 6 in which there is an internal reflection. The reflection surface R1 is suitably inclined so that a portion ofbeam 14 of thefirst laser beam 13 leaving thelight guide 3 through the exit surface Al has a desired direction. - Furthermore, the exit surface A1 is perpendicular to the portion of
beam 14 leaving thefirst branch 6. In this way, the direction of the portion ofbeam 14 leaving thefirst branch 6 is independent of the refractive index of the material of which thelight guide 3 is made. In other words, once a spatial orientation of the reflection surface R1 and that of the reflection surface A1 (perpendicular to the exiting beam) have been defined, it is always possible to change the type of material of the light guide 3 (polycarbonate, acrylic, etc.) without changing the direction of the portion ofbeam 14 leaving thefirst branch 6. - The above considerations apply to the other four branches 7-10 of the
light guide 3, that is to the branches provided with the exit surfaces indicated by reference A2-A5. - These branches too are provided with reflection surfaces, indicated with R2-R5 in FIG. 2—cooperating with the corresponding exit surfaces A2-A5.
- Each branch of the
light guide 3 projects a luminous spot onto the plane of code. In this way, having suitably defined for each branch the spatial orientation of the last reflection surface (indicated by R1 in the case of first branch 6) and of the exit surface (indicated by A1 in the case of first branch 6), a pattern formed by five spots is obtained, four peripheral spots (forming a quadrilateral) and a central spot. The shape and dimension of each of these spots substantially correspond to the shape and dimension of the corresponding exit surface of the respective branch, or to the shape and dimension of the aperture of the diaphragm associated with said branch. - By orienting in a suitable way the reflection surfaces and the exit surfaces of the
first branch 6, thesecond branch 7, thethird branch 8 and thefourth branch 9, a peripheral projection pattern is defined on the plane of code. - Alternatively, instead of a
light guide 3 made of transparent material, a hollowlight guide 3 made of a non-transparent material can be used, while all the internal reflection surfaces (24-26 for branch 6) and all the last reflection surfaces (R1 for thebranch 6 and R2-R5 for the branches 7-10) are coated with, or made of, a reflecting material (e.g. a mirror). In this variant it is not necessary to provide the exit surfaces A1-A5. - Embodiments of the light guide, not illustrated, can comprise more or fewer than five branches.
- In an embodiment, four branches can be provided which generate four spots arranged such as to identify vertices of a quadrilateral. This embodiment is similar to the previously described embodiment, but lacks the central branch, i.e. the
fifth branch 10. - A further embodiment can comprise three branches that generate three spots, two of which are arranged such as to identify opposite vertices of a quadrilateral and a third of which is arranged such as to identify a central area of the quadrilateral. In a further embodiment, the three branches can be arranged such as to identify the three vertices of a triangle.
- A still further embodiment can comprise two branches that generate two spots arranged such as to identify opposite vertices of a quadrilateral.
- The above-described embodiments are particularly advantageous when two-dimensional optical information is to be acquired.
- A still further embodiment can comprise two branches that generate two substantially aligned spots.
- This embodiment is particularly advantageous when linear optical information is to be acquired.
- Three configurations of the
light guide 3 are described herein below, which put in relation the aimingarea 16 with anarea 17 which is framed by thematrix sensor 12, which framedarea 17 is detected by the receivingobjective 11 according to a distance between code to be read and reader. - The orientation of the reflection surface R5 and of the exit surface A5 of the
fifth branch 10 remains unchanged in all the above-described configurations. - As shown in
FIG. 5 , in the first configuration the exit surfaces A1-A4 are so oriented that the pattern projected by the four peripheral branches of thelight guide 3 delimits, on the readingplane 15, a rectangular surface having vertices B1-B4, which identifies the aimingarea 16. - The four laser beams coming out of the peripheral branches of the
light guide 3 intersect each other at a point H, situated on the optical axis of the receivingobjective 11 at a distance h from the receivingobjective 11. In this way it is evident that for code-objective distances greater than h the aiming area B1-B4 is always contained within the reader field of view of the reader (identified inFIG. 5 by a further rectangular surface having the vertices 11-14). In particular, if the point H is between the receiving objective and the exit glass of the reader, the framedarea 17 always contains the aimingarea 16 for every code/reader distance. - Actually, a point exists along the optical axis, at a preset distance from receiving
objective 11, at which the framedarea 17 and the aimingarea 16 substantially coincide. For code/reader distances greater than this preset distance, the relation between the aimingarea 16 and the framedarea 17 is inverted, with the former containing the latter. These distances, typically very long, are not however considered operational distances, so it is reasonable to assert that for each operational code-reader distance the aimingarea 16 is always contained within the framedarea 17. - To clarify better, in
FIG. 5 the spot generated by the fifth branch 10 (that is by the central branch of thelight guide 3 which comprises the exit surface A5) has not been shown on the readingplane 15. Thefifth branch 10 generates a spot that is situated in proximity of the centre of the aimingarea 15. In particular, as shown inFIG. 6 , the spatial orientation of the last reflection surface R5 offifth branch 10 and that of exit surface A5 are such that a fifth laser beam, coming out offifth branch 10, intercepts the optical axis of the receivingobjective 11 at only one point—indicated by C5 inFIG. 613 at a distance c from the receiving objective. Thus the fifth beam is misaligned with respect to optical axis of receivingobjective 11 and generates the spot B5 on the readingplane 15. - As shown in
FIG. 7 , in the second configuration the exit surfaces A1-A4 are oriented in such a way that the pattern projected by the four peripheral branches of thelight guide 3 delimits, on the readingplane 15, a rectangular surface having vertices B1-B4 which identify the aimingarea 16. - The four laser beams coming out of the peripheral branches have no point of intersection. In particular, in this configuration the aiming
area 16 and the framedarea 17 substantially coincide at a distance k from receivingobjective 11. For code-reader distances smaller than distance k, the aimingarea 16 always contains the framedarea 17 while, for code-reader distances greater than distance k, the aiming area 1.6 is always contained within the framedarea 17. - To clarify better,
FIG. 7 does not show the spot generated on the readingplane 15 by the central branch of the guide, the position of which remains unchanged with respect to the first configuration previously described. - With this configuration, the operator using the reading device at code-reader distances smaller than k cannot be certain that a code belonging to aiming
area 16 is really framed and therefore acquired by the reader sensor and then decoded. In fact, a code near an edge of the aimingarea 16 could be left out (also only partially) of the framedarea 17. However, in reading applications at short distances the codes to be read have generally small dimensions and the indication given by the spot generated by the central branch of the guide constitutes a sufficient reference for the operator. - As shown in
FIG. 8 , in the third configuration the exit surfaces A1-A4 are so oriented that the pattern projected by the four peripheral branches of thelight guide 3 delimits, on the readingplane 15, a rectangular surface having vertices B1-B4 which identify the aimingarea 16. - The four laser beams coming out of the peripheral branches intersect each other in pairs, or two by two. In particular, in the third configuration, starting from a distance w from the receiving
objective 11 the aiming area is contained within the framedarea 17. With distances of the receiving objective 11 from the code that are greater than distance w, the framedarea 17 always contains the aimingarea 16, while with distances of the receiving objective 11 from the code which are smaller than distance w it is not possible to be certain whether the framedarea 17 contains, or is contained in, the aimingarea 16. - To clarify better,
FIG. 8 does not show the spot generated on the readingplane 15 by the central branch of the guide, the position of which remains unvaried with respect to the above described first and the second configurations. - Various embodiments of the
light guide 3 are possible. - In one embodiment, shown in
FIG. 11 ,fillings 19 can be inserted within thelight guide 3, said fillings being optically inactive portions arranged for increasing the mechanical resistance of thelight guide 3, leaving unaltered the optically active surfaces. - In a further embodiment, shown in
FIG. 10 , thelight guide 3 can comprise portions of guide having a circular section. - In a further embodiment, shown in
FIG. 9 and inFIGS. 1 to 3 , thelight guide 3 can comprise portions of guide having a square or rectangular cross-section. - In a preferred embodiment, schematically shown in
FIG. 12 , thelight guide 3 comprises portions of guide having a square section of 1.4 mm×1.4 mm. Thelight guide 3, similarly to what is shown inFIG. 11 , comprises optically inactive fillings to increase mechanical stability. - In this preferred embodiment, the exit surfaces A1-A4 of the four peripheral branches of
light guide 3 are arranged according to the first configuration which has been described with reference toFIGS. 5 and 6 . The laser beams coming out of the four peripheral branches of thelight guide 3 intersect one another at the point H′ of the optical axis which is less than 30 mm from the receivingobjective 11. If the distance between receiving objective 11 and exit glass of the reader is greater than h′, the above-mentioned laser beams are always contained within the framedarea 17. The laser beam coming out of the central branch intersects the optical axis at the point C5′ which is approximately 150 mm from the receivingobjective 11. - Having defined all these parameters, the light guide of the preferred embodiment above described has been modelled using the TracePro® ray-tracing simulation program. The results obtained from the simulation program match those calculated during the design process very well. In the simulations it was established that a beam of parallel rays (those coming out of the collimating lens) strikes the five branches and an irradiance map on the plane of code was obtained in, relation to the distance from the objective. The results are illustrated in
FIGS. 13 to 18 . - A comparison between values of x, y coordinates (in mm) of the points B1-B4 (
FIG. 12 ) on the plane of code calculated during design of the light guide, at a distance of 300 mm from the receivingobjective 11, compared with values B1S-B5S (FIG. 18 ) obtained from simulations, gives an extremely good match: -
-
-
-
- Similarly, comparing, at a distance of 150 mm from the receiving
objective 11, the x, y coordinates of the point B5 as per design (FIG. 12 ) with the simulated coordinates B5S (FIG. 15 ), a very good correspondence is obtained: -
- With reference to
FIG. 19 , interior of anoptical information reader 30 is schematically shown. Thelight guide 3, in the preferred embodiment inFIG. 12 , can be fixed inside thereader 30 so as to ensure correct coupling with alaser diode 27 with which thelaser 2 is provided. Reophores oflaser diode 27 are soldered on aPCB 29 on which thesensor 12 is also mounted, which sensor is in turn contained within an optical chamber not illustrated inFIG. 19 . Thelaser diode 27 is mounted perpendicular to thePCB 29 and correct positioning thereof is ensured by atubular element 28 which contains the laser diode and is made for example of a plastic material. In particular, thelaser diode 27 is inserted in afirst end 31 of thetubular element 28. The base of thetubular element 28 is in turn fixed—for example by a pair of screws—to thePCB 29. Thetubular element 28 is longer than the laser diode 27: thus it is possible to insert theentrance end 5 of the light guide 3 (the one provided with the collimation lens 4) within asecond end 32 of thetubular element 28, opposite thefirst end 31. Thelight guide 3 can be held in position with respect totubular element 28 by means of one or more threaded connecting elements or by a special assembly tool (template). The distance between thelaser diode 27 and thelens 4 is such that the laser beam entering thelight guide 3 is well collimated. - There are various ways to obtain a fine adjustment of the
laser diode 27—lens 4 distance, two of which ways are illustrated below in detail. - In a first way, once the reophores of the laser diode have been soldered to the
PCB 29, an assembly tool (template) can be made that is capable of moving thelight guide 3 forwards and backwards so as to identify (and afterwards to fix) anoptimal laser diode 27—lens 4 distance by checking the collimation of the beam coming out of the guide. - A second way consists of fixing the
light guide 3 within thetubular element 28 in such a way that thelaser diode 27—lens 4 distance is near the optimal distance (thelight guide 3 is thus solidly connected to the tubular element 28). Then an assembly tool (template) is used to move thelaser diode 27 backwards and forwards with respect to thePCB 29 by means of the play provided by the length of reophores; once the optimal distance has been found—always by checking the collimation of the laser beam coming out of the light guide—the position of thelaser diode 27 on thePCB 29 is fixed by soldering the reophores. - As a consequence, the use of the
light guide 3 is advantageous in manufacturing the reader 30: thelaser diode 27 is in fact soldered to thesame PCB 29 on which thesensor 12 is also mounted (there is no need for a wiring connection) and the collimation of the aiming device can also be carried out using for example one of the two ways described, also in a “remote” manner with respect to the rest of optic chamber. Alternatively, the optical chamber and the tubular element containing the laser diode could be made in a single piece, moulded in plastic (or cast in metal). - The apparatus for reading optical information comprising the device of the invention in the possible embodiments thereof can be housed in a casing that can be held by an operator and thus be portable, or be in a fixed casing for example for reading applications at points of sale (POS) where the operator passes objects in front of a window of the apparatus for reading optical information, and the optical code to be read faces the window.
- The reading apparatus can also be fixed at a conveyor belt, or other means for transferring objects, for use in industrial optical information reading applications associated to object in motion even at high speeds. Applications of this type can also be used for control of production lines or recognition, tracing and sorting of objects and packages.
- The portable and fixed reading apparatuses can be of the “imager” or the “laser scanner” type.
- Furthermore, apart from the capability to read optical information, the aiming device of the invention can be advantageously used in image acquisition apparatuses in general, where it can be useful to indicate clearly the framed zone to an operator, so that the image acquisition apparatus can be positioned correctly.
- Apparatuses of this type can be for example micro-cameras lacking a display for observing the framed area, or fixed TV cameras for acquiring images of objects in motion on conveyor belts and for determining their size or shape characteristics or for control and surveillance systems.
Claims (52)
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TWI519730B (en) * | 2013-12-30 | 2016-02-01 | 緯創資通股份有限公司 | Light source module |
CN106560835B (en) * | 2015-09-30 | 2019-05-24 | 高德软件有限公司 | A kind of guideboard recognition methods and device |
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- 2006-12-18 EP EP06842251.8A patent/EP2113092B1/en not_active Not-in-force
- 2006-12-18 CN CN2006800566751A patent/CN101563639B/en not_active Expired - Fee Related
- 2006-12-18 WO PCT/IB2006/003689 patent/WO2008075120A1/en active Application Filing
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US7075663B2 (en) * | 1998-10-30 | 2006-07-11 | Datalogic, S.P.A. | Optical device and a method for aiming and visually indicating a reading area |
US20060239006A1 (en) * | 2004-04-23 | 2006-10-26 | Chaves Julio C | Optical manifold for light-emitting diodes |
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US10908076B2 (en) * | 2016-02-24 | 2021-02-02 | Tomra Sorting N.V. | System and method for the detection of acrylamide precursors in raw potatoes and potato-based food products |
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EP2113092B1 (en) | 2014-08-27 |
CN101563639A (en) | 2009-10-21 |
WO2008075120A1 (en) | 2008-06-26 |
US8181877B2 (en) | 2012-05-22 |
EP2113092A1 (en) | 2009-11-04 |
CN101563639B (en) | 2013-04-10 |
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